Position determining apparatus



April 28, 1936. E. s. PURINGTON POSITION DETERMINING APPARATUS FiledApril 29, 1935 I 2 Sheets-Sheet l INVENTOR mm .9 2mm B ATTORNEY P 1936-Q E. s. PURINGTON 2,038,873

POSITION DETERMINING APPARATUS Filed April 29, 1953 2 Sheets-Sheet 2INVENTOR ELLISON RINGTON ATTORN EY Patented Apr. 28, 1936 UNITED STATESPATENT OFFICE POSITION DETERMINING APPARATUS Ellison S. Purington,Gioucester, Mass., assignor to John Hays Hammond, Jr.

Application April 29, 1933, Serial No. 668,482

2 Claims. (01. ass-11) The present invention relates generally to di-Fig. 3 is a diagrammatic showing of an alterrective beacon systems andmore particularly to native form of a portion of the receiver circuit ofa system for guiding vessels, planes or other Fig. 2;

- craft along proper courses. Fig. 4 is a preferred form of theinvention 5 It is an object of the present invention to deusingindirectly heated half wave rectifiers; and, 5 vise a system by whichthrough the medium of Fig. 5 is another form of the invention utilizingtransmitted electrical waves a vessel or the like a single tubearrangement. may be able to determine directly its proper In the presentinvention the two crossed loops course. previously referred to are inreality a pair of It is another object of the present invention'to loopantenna having a common axis. The coils 10 devise means through theoperation of which the of the respective loops are constructed so as topilot of a vessel or the like is advised as to the be at some suitableangle with respect to each direction and extent that the vessel deviatesfrom other. Each loop is energized by continuous high its prescribedcourse. frequency waves, energy received from any par- A further objectof the invention is to provide ticular loop being distinguished fromenergy re- 15 apparatus to transmit directional signals by elecceivedfrom another loop of the system by the trical waves by means of whichvessels, aircraft frequency of the high frequency waves. Prefand thelike may be guided. erably the intensity characteristics of the waves Astill further object of the invention is to transmitted from all theloops are the same, thus provide receiving apparatus for interceptingthe other things being equal, a receiver located on 20 transmittedbeacon energy and derive therefrom a line bisecting the angle formed bythe two the necessary information to indicate to the pilot loop antennaewill receive equal intensity signals the extent and direction ofdeviation, if any, from from both transmitting loops. A receiver locatedthe prescribed course of the vessel. to one side of the angle bisectorwill receive Specific objects of the invention will be apparstrongersignals from one loop and weaker sig- 5 ent from the followingspecification when read nals from the other loop, whereas, a receiverloin connection with the appended drawings. cated to the other side ofthe bisector will receive Briefly, the present invention is based uponweaker signals from the first mentioned loop than the utilization ofcrossed loops for directive transfrom the second loop.

3 mission. In the system disclosed, two crossed It is evident now that avessel provided with loops are respectively energized by differentfresuitable receiving apparatus for receiving sigquency continuous Wavesto give the desired disnals from both loops and also provided withsuittinguishing characteristics. Consequently, the able signal intensityc pa indicating system involves the receipt of the transmitted meanswhich preferably takes the form of a difcontinuous waves by continuouswave receivers, ferential indicator, may be steered or guided 35 afeature of the invention which results in paralong a definite courseeven in foggy weather. ticularly eflicient operation. Thus if the courseto be followed is in fact the The present invention should bedistinguished angle bisector, that is, the line or zone of equal fromknown directive beacon systems utilizing signal intensity, the pilotwould steer the craft 4o crossed loops all transmitting waves of thesame so that the signal intensity indicator would indifrequency butmodulated by difierent audio frecate receipt of equal intensity signalsfrom each quencies for providing the necessary distinguishof the twotransmitting loops of the system. The ing characteristics. In the lattertype much pilot is able to recognize that he is off his course, troubleis met with in designing proper and eflithat is to say, off the line orzone of equal signal cient apparatus especially when visual recordingintensity by the fact that the signal intensity com- 5 is contemplatedbecause of difiiculties encountered paring device or indicatorshows thereceipt of unin the required selective systems. equal intensity signalsfrom the two loop trans- In the drawings, mitters. Fig. 1 illustratesschematically a directive In other words, under these conditions thediftransmitting system which may be utilized in conferential indicatoris, so to speak, off balance, the 50 nection with the present invention;extent it is oif balance to one side or the other Fig. 2 is adiagrammatic representation of a of the balance point showing the pilotthe extent preferred type of receiver used for receiving siganddirection of deviation from the intended nals transmitted from asystemsuch as shown in course.

Fig, 1; In Figure 1, a beacon transmitter system is 55 shown ascomprising a pair of crossed loop antennaa I and IN energized by thedifferent frequency high frequency generators or sources I02 and I03respectively. The line 00 passing through the common axis of the twoloops I00 and HII is the previously referred to line of equal signalintensity. Thus with equal intensity energy transmitted from the twoloops I00, HH and other things being equal, a receiver located on theline 00, as for instance on the airplane I04, would receive equalintensity signals from the two loop transmitters. vA receiver located onthe plane I05 would then receive stronger signals from loop IOI thanfrom loop I00, whereas, a receiver located on plane I06, would receivestronger signals from loop I00 than it would receive from loop IOI.Also, the ratio of signal intensity of signals received from antenna IOIand signals received from antenna I00 at I05 is much less than the ratioof signal intensity of signals received from antenna I00 and signalreceived from antenna IOI at I06 because of the fact that plane I06 isfurther away from the line or zone of equal signal intensity 00 than isplane I05. However, the oil balance conditions of the indicator would bein one direction with regard to the balance point at I05 and in theother direction at I00.

It is obvious that the two loops I 00 and IM may be rotated about theircommon axis so as to fix the zones of equal signal intensity in anydesired direction.

The receiver shownlin Fig. 2 comprises antenna I and counterpoise 2adapted to impress energy intercepted thereby upon the input circuit ofa space discharge device I0. The input circuit comprises a tuned circuit5 which includes inductance coil 3 and tuning condenser 4 adjusted so asto be bi-resonant, that is, equally responsive to the two frequencies asgenerated at I02, I03 (Fig. 1) and transmitted by the two loops I00 andIM respectively.

Tube I0 is in reality a mixing tube deriving this characteristic byreason of the grid condenser, grid leak arrangement 9, 8 respectively.Tube I0 also is provided with the usual output circuit comprisinginductance II, shunted condenser I3 and anode potential source indicatedas B+. Coupled to the coil 3, through suitable coil '6 is a source ofpeferably constant frequency oscillations I. It is obvious now, sincetube I0 is a mixer tube, that energy impressed across coil 3 from theantenna counterpoise I, 2 is combined with the energy generated at I andin the output circuit of tube I0 there exist what are known as beatfrequencies resulting from combining the various frequencies impressedupon the input of the tube. Since three frequencies are impressed uponthe input circuit 5, namely, oscillations from generators I02 and I03and oscillations from source I, it is obvious that the output circuit oftube I0 will include several beat frequencies. Among the beatfrequencies that stand out are the sum and difference of the frequenciesof I02 and I and the sum and difference of the frequencies of I03 and I.For example, if it is assumed that generator I02 produces oscillationsof frequency equal to 303,000 cycles per second, generator I 03 producesoscillations having a frequency equal to 297,000 cycles per second andsource I oscillations having a frequency equal to 323,000 cycles then itis seen that in the output of tube I 0 there will be present amongothers oscillations of 26,000 cycles per second and 20,000 cycles persecond. The 26,000 cycles energy may then be said to be representativeof the energy transmitted by loop iei, whereas, the 20,000 cycles energyis representative of the energy transmitted by loop I00, and these twofrequencies are isolated from the rest of the other beat frequencies andallowed to pass to an amplifier circuit IT from. the output of tube I0.The input of the amplifier I6 comprises a tuned circuit includinginductance coil I2 and tuning condenser IS.

The circuit comprising coil I I and condenser I3 and the circuit coupledthereto comprising coil I2 and condenser I6 are preferably made so as topresent double resonance characteristics, that is, the two circuitsresonate equally to the two frequencies 20,000 cycles and 26,000 cycles.Amplifier Il may comprise one or more stages of cascaded amplifier tubesconnected in any of the well known methods such as resistance,impedance, transformer, direct and/or capacitive coupling. The outputcircuit of the amplifier I! which may be the output circuit of the laststage thereof includes a pair of tuned circuits I8 and I9. Circuit I 8comprising an inductance coil 22 and a shunted condenser 2I is resonantto 20,000 cycles and will, therefore, isolate the amplified oscillationsof that frequency. Circuit I9 comprising coil- 23 and tuning condenser20 is tuned to a frequency of 26,000 cycles, hence, this circuit willtend to isolate the amplified oscillations of that frequency. It followsthat tuned circuits I8 and I9 separate the two frequencies fed into theinput of amplifier I! after both are amplified. The amplified 20,000cycle oscillations are then impressed upon a similarly tuned circuit 29which comprises an inductance coil 25 and a tuning condenser 26 whilethe amplified 26,000 cycle oscillations are impressed upon circuit 28tuned to resonate at 26,000 cycles by coil 24 and condenser 21.

Tuned circuit 29 forms part of a. series circuit which includes a sourceof current 60, a winding 38 and a power type rectifier 30. It is seenthen that the energy impressed upon circuit 29 from circuit I8 is, inefiect, rectified by tube 30 so that there flows a current through coil38 as indicated by the arrow the intensity of which is, in fact,proportional to the intensity of the energy intercepted by antenna Itransmitted by loop I00. Tuned circuit 28 similarly forms part of aseries circuit which includes source 6|, winding 39 and power typerectifier 3I.

Consequently, the energy impressed upon circuit 28 from circuit I9 isrectified by tube 3I and there flows a current through winding 39 in thedirection indicated by the arrow the intensity of which is proportionalto the intensity of the energy intercepted by antenna I transmitted byloop IOI.- Windings 38 and 39 may form part of a double winding ammeterthe component parts of which comprise an iron u -shaped core 32 thecenter of which is magnetically grounded on the opposite legs of whichthe windings 38 and 39 are wound, a balanced polarized armature 33pivoted about a point 36 preferably at its midpoint, a balancing spring35 arranged with respect to armature33 so as to tend to maintain thearmature at its mean position, an indicator needle 34 fixed to armature33 and a cooperating scale 31. The ammeter is preferably arranged sothat current flowing in winding 38 magnetizes core 32 in a sense that ittends to rotate armature 33 counterclockwise about pivot point 36against the action of spring 35 while current flowing in winding 39magnetizes core 32 in a sense to rotate armature 33 clockwise againstthe action of spring 35. It

is obvious then that with equal current flowing 76 2,038,878 in bothwindings 38 and 33 as when the receiver is located on craft ")4 (Fig. 1)armature 33 is not rotated and needle 34 reads zero on scale 81. Withthe receiver on plane I the current flow in winding 38 would be lessthan the current flow in winding 39, hence, needle 34 would swingclockwise a comparatively small amount determined by the ratio of theintensity of the two currents. The needle 34 on a receiver located onplane I06 would swing counter-clockwise a. comparatively large amount asdetermined by the ratio of the intensities of the two currents flowingin windings 38 and 39 of the particular receiver on plane Hit.

It is obvious from what has preceded that to obtain useful readings asto the course of the craft upon which the receiver system shown in Fig.2 is located, it is preferable to construct the two branch circuitswhich include the tubes 30 and 3| so that they have substantially thesame characteristics. While it is a comparatively simpie matter toconstruct two circuits having similar characteristics, it is a fact thattubes having suificiently similar characteristics throughout theoperating ranges are not so easily constructed in quantity production.Consequently, A matched tubes entail greater expense and inconvenience.To overcome this drawback, the system shown in Fig. 3 is presented. Inthis system in place of two detector tubes 30 and 38 there is provided asingle tube 50 which is composed of a single cathode 53 and two anodes5i and 52. The cathode 53 is energized by a suitable source 56;connected across the cathode. Only-that portion of the complete circuitis shown in Fig. 3 as is necessary for a proper understanding of thedevice. Thus, it will be noted that tuned circuits 28 and 29 of Fig. 3correspond to the tuned circuits 28 and 29 of Fig. 2, sources 53 and iiiof Fig. 3 correspond to sources 50 and 6! of Fig. 2, core 32 of Fig. 3is the same as core 32 of Fig. 2 and the windings 38 and 39 are alsosimilar in both figures. In order to connect the tube 50 to bothcircuitsthere is provided a resistance 55 which is shunted across thecathode and the connection to both anodes is made through a conductor 56from a point of the resistance 55. It-should be noted that the conductor56 is provided with an adjustable element for tapping on to theresistance 55. This is for the purpose of adjustment whereby the twocircuits may be made symmetrical with respect. to both windings 33 and39 ing the transmitted waves including an antenna lit is believed to beobvious from whathas thus far been described that the energy impressed,upon circuit 29 is rectified by the tube 55 and flows through thewinding 38 in the direction of the arrow. Energy'impressed upon circuit28 is also rectified by the tube 5d and this energy passes through thewinding 89 as indicated-by the arrow, the current flow in each circuitbeing as follows:

From tube circuit 29 through the source 6i), through winding 38, toplate 3 i, to the cathode 53, through conductor 56 back to tuned circuit23 for the first case and from tuned circuit 28 through source 6 I,through winding 3d, to plate 53, to cathode 53 and back to the tunedcircuit 28 through conductor 56 for the second case. It is obvious nowthat the windings 3B and 39 of Fig. 3 are afiected by the energyimpressed upon tuned circuits 29 and 28 in the same manner that thewindings 38 and 39 of Fig. 2 are affected by the energy impressed upontuned circuits 29 and 28 of said Fig. 2.

In Fig. 4, a slightly difierent circuit i 3 limit is shown wherein thereadings are provided by a meter 200 which'may be a commercial type D.C. instrument with pointer in the center and capable of either rightorleft deflection. 30 and 3| are half wave rectiflers having indirectlyheated cathodes. The heater circuit for bothtubesis supplied by asuitable source shown for convenience as a battery 202. Resistance 2Mgrounded at its midpoint is shunted across the instrument. Current flowsthrough resistance 2M from each tube as indicated by the arrows. It isto be understood that copper oxide rectiflers may be substituted for thetubes shown in the drawings.

The system shown in Fig. 5 is the same as Fig. 4 except that a singletube 203 is provided having two anodes and two indirectly heatedcathodes. The single heater circuit ior the two cathodes is connected tothe terminals 2.

Since the operation of the system disclosed by applicant is believed tohave been made clear from the above description of the various circuitsa detailed discussion will be omitted.

In practice, the meter scale 3? may read for example on course when atzero indication, north of course for deflections of theneedle 33 in onedirection and south of course for deflections of the needle in theopposite direction. It is to be understood that any suitable type ofindications may be provided, in fact, the choice thereof is solelydependent on the wishes of the designer and the pilot.

Applicant desires it'to be understood that the particular values of thevarious frequencies chosen above are solely for purposes of illustrationand not limitation and further that any suitable values of thesefrequencies may be chosen.

I claim:

1. In a system for transmitting and translating directive radio signalsof the type provided with means for producing two diiferent frequencybut equal amplitude continuous radio frequency waves, meansforindependently and directionally transmitting said waves, comprising twocrossed loop antennae the combined transmission characteristics of whichproduce at least one zone of equal signal intensity and means forpredetermining the spacial location of said zone, means for locating aparticular receptionpoint with respect to the zone of equal signalintensity comprising in combination, means for interceptarrangementhaving equal reception characteristics for all of said transmitteddifferent frequency waves, a source of constant frequency oscillationsdifiering from the frequency of each of the trans-' mitted waves, acombining circuit for mixing the received energy waves with energy fromsaid source, a selector circuit for selecting at least one product fromthe combination of each energy wave with energy fromthe source, meansfor segregating each of the selected products, means for separatelyrectifying the segregated products, means for producing from therectified segregated products equivalent magnetic forces, means forcombining these magnetic forces in a sense to compare their respectiveintensities and means for producing a single indication of theirrelative intensities. I

2. In a system for comparing the relative intensities of two radiofrequency waves." a source of auxiliary frequency energy diifering infrequency from the frequency of the two waves to be compared, acombining circuit for mixing the two radio frequency waves with theauxiliary trequency energy, a selector circuit means arranged so as toselect at least'one product from-the combination of each radio frequencywave with the auxiliary frequency energy, means for segregating each ofthe selected products, means for separately detecting the segregatedproducts, means for transforming each of the products of said detectioninto equivalent magnetic energy, means for combining the resultantmagnetic energies in a sense to compare their respective intensities andmeans for producing a single indication of their relative intensities,

ELLISON s. PURINGTON'.

